osx new filter in ppd not called

[atze]

hi all,
i added a new filter for multitray handling in my ppd (hplj4000).

*APPrinterIconPath: "/Library/Printers/hp/Icons/HP LaserJet 4000 Series.icns"
*cupsFilter: "application/vnd.cups-postscript 0 /Library/Printers/hp/filter/hpPostProcessing.bundle/Contents/MacOS/hpPostProcessing"
*cupsFilter: "application/vnd.cups-postscript 0 trayfilter"

This works really nice on my ubuntu (cups 1.4.1) but on osx (cups 1.3.11) the filter doesn't seem to get called:

I [19/Feb/2010:11:22:14 +0100] [Job 48] Started filter /usr/libexec/cups/filter/pstops (PID 3366)
I [19/Feb/2010:11:22:14 +0100] [Job 48] Started filter /Library/Printers/hp/filter/hpPostProcessing.bundle/Contents/MacOS/hpPostProcessing (PID 3367)
I [19/Feb/2010:11:22:14 +0100] [Job 48] Started backend /usr/libexec/cups/backend/usb (PID 3368)

Does anyone know what I am missing here?
greets, andreas.